Tuesday, 29 November 2016

Two miles of ice melt in one day?

Did
Föhn Winds Just Melt Two Miles of East Antarctic Surface Ice in
One Day?

It’s
right there in the satellite image. A swatch of blue that seems to
indicate an approximate 2-mile long melt lake formed over the surface
of East Antarctica in just one day. If confirmed, this event would be
both odd and concerning. A part of the rising signal that melt
stresses for the largest mass of land ice on the planet are rapidly
increasing.

(Possible
large melt lake on the surface of an ice shelf along the Scott Coast
appears in thisNASA
satellite image.
The melt lake seems to have formed after just one day during which
föhn winds ran downslope from the Transantarctic Mountain Range —
providing a potential period of rapid heating of the glacier
surface.)

But
now, even in austral springtime, we find evidence of surface melt in
the satellite record.

On
November 27, 2016, what looks like an approximate 2 mile long melt
pond appeared in a section of ice shelf along the Scott
Coast and
just North of the Drygalski
Ice Tongue in
the region of McMurdo Sound. The lake — which is visible as a light
blue swatch at center mass in the NASA-MODIS satellite
image above — suddenly showed up in November 27 satellite image
along a region where only white ice was visible before. And it
appears in a region of East Antarctica that, before human-forced
warming altered the typically-stable Antarctic climate, had rarely,
if ever, seen surface melt.

Supraglacial
lake is just another word for a surface glacial melt lake. And these
new lakes pose a big issue for ice sheet stability. Surface melt
lakes are darker than white glacier surfaces. They act as lenses that
focus sunlight. And the comparatively warm waters of these lakes can
flood into the glacier itself — increasing the overall heat energy
of the ice mass.

(A
NASA researcher investigates a surface melt pond in Greenland. During
recent years, these climate change related features have become more
common in Antarctica. Image source: NASA.)

Now,
a similar process is impacting the largest concentration of land ice
on the planet. And while Greenland holds enough ice to raise sea
levels by around 21 feet, East Antarctica contains enough to lift the
world’s oceans by about 195 feet. Surface melt there, as a result,
produces considerably more risk to the coastal cities of the world.